Comparisons of nutritional constituents in soybeans during solid state fermentation times and screening for their glucosidase enzymes and antioxidant properties

Abstract

This research was the first to demonstrate the variations of nutritional constituents, glucosidase properties and antioxidant activities in soybeans during different solid state fermentation times (germination -> 5 periods for 12 days) with Tricholoma matsutake. Total isoflavones were significantly reduced (2661.54 -> 1559.04 mu g/g) with the increase of aglycone contents (107.61 -> 1285.66 mu g/g, 12 times) for fermentation, whereas amino acid and fatty acid slightly increased. Among them, daidzein (43.2 -> 43.6 -> 421.9 -> 721.4 -> 634.0 mu g/g), genistein (52.7 -> 24.4 -> 339.5 -> 546.6 -> 512.8 mu g/g) and glutamic acid (0.3 -> 1.7 -> 3.9 -> 6.6 -> 16.1 mg/g) markedly increased between germinated and fermented soybeans. Total phenolic contents and antioxidant abilities also considerably increased, especially, ABTS displayed the predominant scavenging capacities (33.1 -> 94.8%) at 200 mu g/ml, followed by DPPH (11.9 -> 87.0%) and hydroxyl (11.2 -> 49.2%) radicals. Interestingly, alpha-glucosidase inhibition (11.8 -> 84.9%) and beta-glucosidase (3.1 -> 40.3 unit/g) exhibited the highest activities after 9 days. Our results implied that fermented soybeans may be contributed to enhance the soybean value in nutrition and biological effect aspects to development of new functional foods.